JP4942118B2 - Leakage detection system for heat exchanger in hot water heater - Google Patents

Description

  The present invention is directed to a leak detection system for a heat exchanger in a heating hot water supply apparatus that heats a heat load with a heat medium heated by a heat source and circulates the heat medium between the heat source and the heat load, i.e. This relates to a water leakage detection system that detects internal leaks (leakage) in a heat exchanger that heats the secondary hot water, and it is possible to deaerate the secondary circulation circuit and misdetect an overflow caused by air ingress as an overflow due to water leakage The detection accuracy with water leakage can be improved for the water leakage detection.

The primary side hot water is circulated in the primary circulation circuit between the heat source and the heat exchanger, and the secondary side hot water is circulated in the secondary circulation circuit between the heat exchanger of the primary circulation circuit, the open tank and the heat load, and the secondary circulation. A water leakage detection system for detecting an internal leak (water leakage) of the heat exchanger in a heating hot water supply apparatus that heats a heat load with secondary hot water of a circuit is known, and an example thereof is Japanese Patent Application Laid-Open No. 2004-251888 (Patent Document). 1), and Japanese Patent Application Laid-Open No. 2003-114056 (Patent Document 2).
The outline of the heating and hot water supply apparatus of Patent Document 1 is shown in FIG. 3, and includes, for example, main heating means such as a thermoelectric supply apparatus and auxiliary heating means such as a gas water heater, and further a hot water storage tank. The primary hot water circulates through these. The primary circulation circuit includes heat exchangers 100 and 100, and the heat exchanger 100 heats the heat medium of the secondary circulation circuit, that is, the secondary hot water. The secondary circulation circuit for the terminal circulates between the heat exchanger 100, a terminal device such as a heating radiator and the open tank T, and the secondary circulation circuit for the bathtub circulates between the heat exchanger 100 and the bathtub. .

The primary side hot water in the primary circulation circuit is also used for hot water supply. On the other hand, the secondary side hot water circulating in the secondary circulation circuit for the terminal is not clean water. The pressure of the secondary circulation circuit is set lower than the pressure of the primary circulation circuit so that the secondary-side hot water does not enter the primary-side hot water even if leakage or water leakage occurs. The secondary circulation circuit is opened to the atmosphere in the open tank T.
The open tank T is provided with a low water level switch L, a high water level switch H, and an overflow switch O that detect three water levels of a low water level, a high water level, and an overflow water level, respectively.
When the amount of secondary hot water increases due to water leakage, air intrusion, thermal expansion, etc. of the heat exchanger 100, the water level of the open tank T rises. Then, when the water level in the open tank T rises and reaches the overflow water level, it is detected by the overflow switch O and an error is displayed. On the other hand, when the amount of secondary side hot water decreases due to evaporation or the like, the water level of the open tank T decreases, and when this reaches a low water level, it is detected by the low water level switch L, the water supply valve is opened, and the high water level switch H is turned ON. It is replenished from the water pipe. As a result, the water level of the open tank T is maintained between the low water level and the high water level, and an error is displayed when the water level rises to the overflow water level for some reason such as water leakage.

In the above prior art, the secondary side hot water is used for the invasion of air into the secondary circulation circuit (infiltration of air from piping, etc.), the expansion of the secondary side hot water, the inflow of the primary side hot water due to the leakage of the heat exchanger's narrow tubes, etc. The volume of increases. When the volume of the secondary medium increases in this way, the water level of the open tank T rises and eventually overflows. When overflow occurs, this is detected by the overflow switch O and an error is displayed.
The leak detection of this prior art is to detect a leak in the narrow tube of the heat exchanger 100 (leakage to the secondary side hot water of the primary side hot water). This is done by the ON / OFF signal of the overflow switch O of the open tank T, but it does not immediately cause a water leak by the ON signal of the overflow switch O, but it indicates whether it is an air intrusion when the overflow switch O is turned on. When it is confirmed that it is not caused by air intrusion, it is determined that there is water leakage. The water leakage detection operation is performed as follows (see FIG. 4).
(A) When the overflow switch O is ON, the circulation pump of the secondary circulation circuit is operated and deaerated (FIG. 4 (a)).
(B) The rise in water level is monitored for a predetermined time (FIG. 4 (c)).
(Detects the presence or absence of capillary leaks based on the presence or absence of water level recovery for a specified time)
(C) When the overflow switch O remains ON, it is determined that there is water leakage (FIG. 4B).
(It turns out that there is no deaeration)
(D) When the overflow switch O is once turned off and then turned on, it is determined that there is water leakage (FIGS. 4C and 4D).
(It was found that the water level drop due to deaeration was recovered by water leakage for a predetermined time with deaeration.)
(E) When the overflow switch O is once turned off and remains off, it is determined that there is no water leakage (FIGS. 4C and 4E).
(Degassed, it turns out that there is no water leakage enough to recover the water level drop due to the degassing in a predetermined time)

[Problems of the prior art]
In the above prior art, since the overflow switch O is ON and the circulation pump P of the secondary circulation circuit is driven to perform the deaeration operation, if the deaeration amount is small once deaeration, the water level at that time However, if the water level at that time is high and close to the water level at which the overflow switch O is turned on, the overflow switch O may be turned on due to a short air intrusion. In the case where there is no water leakage in the heat exchanger, the overflow switch O is turned on by the entry of a small amount of air and the deaeration operation is performed, the water level is lowered and it is determined that there is no water leakage, and then the overflow switch O is repeatedly performed. Is turned on and deaeration operation is performed.

On the other hand, the volume of the secondary hot water may expand due to temperature rise despite the absence of air intrusion. In this case, the overflow switch O is repeatedly turned on during the expansion process, and each time It is determined that there is water leakage.
In addition, the water level in the open tank T during and after the deaeration operation is affected by fluctuations in the amount of air contained, increase / decrease in the volume of secondary hot water, and increase / decrease in the volume of the secondary circulation circuit. Is constantly fluctuating.
Therefore, ON-OFF-ON of the overflow switch O of the open tank T in the water leakage detection operation does not necessarily indicate a fluctuation in the water level due to deaeration and water leakage, and the overflow switch O may be turned on for a reason other than water leakage. For this reason, it may be erroneously determined as “there is water leak”.
Therefore, when the water level returns until the overflow switch O is turned on again after the deaeration operation after the overflow switch O is turned on, the conventional water leakage detection method that determines that there is water leakage is not necessarily highly accurate.
JP 2004-251888 A Japanese Patent Laid-Open No. 2003-114056

  For systems that detect leaks in heat exchanger capillaries using the ON / OFF signal of the water level switch of the open tank, avoiding frequent deaeration operations and increasing the accuracy of the determination of leakage Reduce false positives.

The means taken to solve the above problems is to circulate the primary hot water in the primary circulation circuit between the heat source and the heat exchanger, and to perform the secondary circulation between the heat exchanger, the open tank and the heat load in the primary circulation circuit. A hot water supply device that circulates secondary hot water in the circuit with a secondary circulation pump and heats the heat load with the secondary hot water in the secondary circulation circuit, where the primary hot water is more pressurized than the secondary hot water The open tank has a low water level switch, a high water level switch, and an overflow switch, and automatically replenishes the water level between the low water level and the high water level detected by the low water level switch and the high water level switch. The following (a) to (f) are based on the premise of the leak detection system for the heat exchanger in the heating hot water supply apparatus that displays an error when the water level detected by the overflow switch is reached.
(B) Check the ON / OFF of the high water level switch every predetermined inspection period (for example, once / week)
(B) When the high water level switch is ON, the secondary circulation pump is driven for a short time for deaeration operation,
(C) The presence / absence of a rise in water level is monitored for a predetermined time (eg, 10 minutes) by turning on / off the overflow switch,
(D) When the overflow switch remains ON, it is determined that there is water leakage.
(E) When the overflow switch is turned on after being turned off, it is determined that there is water leakage,
(F) It shall be determined that there is no water leakage when the overflow switch remains OFF.

Note that the “predetermined inspection period” is shorter than the period during which the overflow switch may be turned on due to the increase in the amount of secondary side hot water due to the amount of air intrusion within the inspection time. It hits.
In addition, the secondary side hot water of the secondary circulation circuit makes a round at least once in the short time, and air mixed in the hot water is released to the atmosphere in the open tank, and the secondary circulation circuit is deaerated. For example, in a hot water supply apparatus installed in a general household, it is about 1 to 2 minutes, although it varies greatly depending on the configuration of the secondary circulation circuit.

In addition, the above-mentioned predetermined time is a time when it is expected that the water level decrease due to the periodic deaeration will be sufficiently recovered by the leakage when there is a minimum allowable capillary leak. In the heating hot water supply apparatus installed in No. 1, this corresponds to approximately 10 minutes.
Therefore, specifically, the above solution means periodically checking whether or not the high water level switch is ON at intervals of one week, and when the high water level switch is ON, drive the secondary circulation pump for 1 to 2 minutes. Perform deaeration operation, check ON / OFF of overflow switch O, check ON / OFF of overflow switch O after 10 minutes, and change the ON / OFF of overflow switch O during this time The presence or absence of a capillary leak will be determined.

When the high water level switch is ON, the secondary circulation circuit is periodically deaerated at a predetermined interval, so that the influence of the air intrusion on the water level of the open tank is almost always eliminated. For this reason, the overflow switch is not turned on.
Therefore, as in the prior art, the overflow switch is turned on due to air intrusion, whereby the secondary circulation pump is driven to perform the deaeration operation, and then it is determined that there is no water leakage. There is no such thing as frequent degassing due to air intrusion, as in the case of air driving.

In addition, the fluctuation of the water level due to uncertain factors such as the thermal expansion of the heat medium (secondary hot water) and the volume expansion of the circulation circuit is smaller than the difference in volume between the high water level and the overflow water level. Therefore, the overflow switch is not turned ON solely due to air intrusion.
Therefore, when the overflow switch is turned on, it almost certainly indicates “there is water leak”. Furthermore, when the overflow switch remains on or after turning off, it is determined that there is water leak. The detection accuracy is extremely high.

Next, an embodiment of the present invention will be described with reference to FIG.
This embodiment is based on a combined heat and power supply device 1, a hot water supply unit 2 and a control device 3. The hot water supply unit 2 includes a hot water storage tank 4 and a hot water supply device 5. The hot water storage tank uses the combined heat and power supply device 1 and the hot water supply device 5 as heat sources. 4 store hot water.
The hot water storage tank 4 serves as a heat source for reheating bath water in addition to hot water supply to the bathroom, kitchen, and the like, and includes a heat medium circulation circuit 6 for heat load such as a heater.
The heat medium circulation circuit 6 supplies hot water to the heat load A and the heat load B, and includes a heat exchanger 61, a primary circulation pump P1, a secondary circulation pump P2, on-off valves V1 and V2, and an open tank 62. Yes. The discharge amount of the primary circulation pump P1 is 10 liters / minute, the discharge amount of the secondary circulation pump P2 is about 2 liters / minute per floor mat, and the secondary circulation pump P2 is operated for about 1-2 minutes. The hot water in the secondary circuit circulates at least once.

The primary side of the heat exchanger 61 is a circulation circuit that circulates hot water in the hot water storage tank 4, and the secondary side is a circulation circuit that circulates secondary side hot water in the heat loads A and B. The relationship between the primary side pressure p1 and the secondary side pressure p2 is p1> p2, and when water leaks in the heat exchanger 61, the secondary side hot water flows into the primary side circulation circuit and flows into the hot water. To avoid doing that.
A water supply pipe 63 is connected to the open tank 62 of the heat medium circulation circuit 6, and water is supplied by the water supply valve V3. The open tank 62 includes a low water level switch L, a high water level switch H, and an overflow switch O. The control device 3 receives the detection signals from the low water level switch L and the high water level switch H to open and close the water supply valve V3. The heat medium level is maintained within the required water level.
The overflow switch O detects the water level when the water level of the open tank 62 rises abnormally and overflows.
The difference in capacity of the open tank 62 between the low water level and the high water level is 0.8 liter, and the capacity difference of the open tank 62 between the high water level and the overflow water level is 0.8 liter.

The primary hot water circulates through the hot water storage tank 4 and the heat exchanger 61 by the circulation pump P1 of the heat source. When the on-off valves V1 and V2 that control the supply of the heat medium to the heat loads A and B are opened and the secondary circulation pump P2 is activated, the heat loads A and B are activated, and the pressure increase and temperature of the circulation circuit The heating medium level of the open tank 62 fluctuates due to an increase or the like.
When a narrow tube leaks, that is, water leaks in the heat exchanger 61, the primary hot water flows into the secondary circulation circuit and the amount of the secondary hot water increases. For this reason, the water level in the open tank 62 rises. When the water level reaches the overflow water level, this is detected by the overflow switch O.
There is provided a water leakage detection means for detecting water leakage of the heat exchanger 61 by detecting an increase in the secondary side hot water due to leakage into the secondary side hot water of the primary side hot water.
Even in the secondary circulation circuit, the water level of the open tank 62 is monitored. When the water level becomes lower than the low water level, the water supply is started and the water level is raised to the high water level, and if the overflow switch is turned on, an error is displayed.
The above is within the scope of technical matters generally provided by the prior art.

The water leakage detection means of the present invention detects the water level fluctuation of the open tank 62 with the low water level switch L, the high water level switch H, and the overflow switch O, and detects water leakage of the heat exchanger 61 based on these detection signals. The leak detection is performed as follows.
However, when the secondary circulation circuit is operated, water leakage detection according to the present invention is not performed.

When water leakage detection starts while the secondary circuit is not operating, the high water level switch H is periodically checked for ON / OFF at weekly intervals (see FIG. 2). At this time, if the high water level switch H is OFF, the water leakage detection is not executed. If the high water level switch H is ON, water leakage is detected by the following procedures (1) to (6).
(1) The secondary circulation pump P2 of the secondary circulation circuit is turned on and operated for 2 minutes for deaeration (case 1, FIGS. 2-1 (b), (c), case 2, FIG. 2-2 (b ), (C) ).
(2) After the secondary circulation pump P2 is stopped, ON / OFF of the overflow switch O is monitored for 10 minutes.
(3) It is determined that there is water leakage when the overflow switch O remains on during monitoring or when it is turned on after being turned off (case 1, FIGS. 2-1 (d), (f)).
(4) When the overflow switch O is turned off during monitoring and is turned on, it is determined that there is water leakage (case 2, FIGS. 2-2 (g) and (f)).
An error is displayed when it is detected that there is water leakage in the above water leakage detection.
(5) If the overflow switch O remains OFF during monitoring, it is determined that there is no water leakage (case 1, FIGS. 2-1 (e) and (g)).
(6) If the overflow switch O remains OFF during monitoring, it is determined that there is no water leakage (case 2, FIGS. 2-2 (d), (e), (h)).

The maximum speed and amount of air entering the secondary circulation circuit depends on the configuration of the piping (equipment layout, piping length, pipe material, etc.).
The secondary circulation circuit in this embodiment assumes that a maximum of 0.4 liter of air may be mixed in one week, and this maximum air mixing raises the water level of the open tank 62 by approximately 5 cm. It is assumed that
By operating the secondary circulation pump P2 for 2 minutes, the secondary-side hot water in the secondary circulation circuit circulates at least once and passes through the open tank 62 at least once and is completely deaerated. .
If the intrusion of air into the secondary circulation circuit is zero, the water level drop of the open tank 62 after the deaeration operation is zero, but if there is intrusion of air, the open tank 62 is commensurate with the amount of air intrusion. The water level of the water drops.
Therefore, if the maximum air amount is mixed in, the water level in the open tank 62 is reduced by about 5 cm due to this deaeration.

  When there is a narrow tube leak (leakage) in the heat exchanger 61 and the water level of the open tank 62 rises to the overflow water level due to the water leak for 10 minutes, the overflow switch O is turned on. It will be determined that there is. Even if there is water leakage, it is not judged that there is water leakage unless it is small enough to turn the overflow switch O from OFF to ON, but since it is regularly inspected at weekly intervals, there is no safety problem.

Is a schematic diagram showing the overall configuration of the embodiment Is a flow chart of leakage detection in the embodiment Is an explanatory diagram of case 1 of the water leakage detection operation in the embodiment Is an explanatory diagram of case 2 of the water leakage detection operation in the embodiment Is a schematic diagram showing the overall configuration of a conventional example Is a reference diagram showing the state of the water level of the open tank in the leak detection system in the conventional example

Explanation of symbols

1: Combined heat and power supply device 2: Hot water supply unit 3: Control device 4: Hot water storage tank 5: Hot water supply device 6: Heat medium circulation circuit 61: Heat exchanger 62: Open tank 63: Water supply pipe A, B: Heat load L: Low water level Switch H: High water level switch O: Overflow switch p1: Primary side pressure p2: Secondary side pressure P1: Primary circulation pump P2: Secondary circulation pumps V1, V2: On-off valve V3: Water supply valve

Claims (3)

The primary hot water is circulated in the primary circulation circuit between the heat source and the heat exchanger, and the secondary hot water is circulated by the secondary circulation pump in the secondary circulation circuit between the heat exchanger, the open tank and the heat load in the primary circulation circuit. A heating hot water supply device that circulates and heats the heat load with the secondary side hot water of the secondary circulation circuit, where the primary side hot water has higher pressure than the secondary side hot water, and the open tank has a low water level switch, When there is a water level switch and an overflow switch, the water level is automatically compensated so that the water level is between the low water level and the high water level detected by the low water level switch and the high water level switch, and the water level detected by the overflow switch is reached. In the water leak detection system of the heat exchanger in the heating hot water supply device where an error display is made,
Check whether the high water level switch is ON every predetermined inspection period,
When the high water level switch is ON, the secondary circulation pump is driven for a short time to perform deaeration operation.
Then, the presence or absence of level rise predetermined time Ma監 viewed by ON / OFF of the overflow switch,
When the overflow switch remains ON, it is determined that there is water leakage.
When the overflow switch is turned on after being turned off, it is determined that there is water leakage.
A water leakage detection system characterized by determining that there is no water leakage when the overflow switch remains OFF.   The water leakage detection system according to claim 1, wherein the predetermined inspection period is one week.   The water leakage detection system according to claim 1 or 2, wherein the predetermined time is 10 minutes.

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